Many razor cartridges include shaving aids, commonly referred to as lubrication strips. These lubrication strips are typically present behind the blades in an aft position such that as a user performs a shave stroke, the skin is contact by the blades prior to contact by the shaving aid. Many different types of shaving aids have been disclosed. See e.g., U.S. Pat. Nos. 7,121,754; 6,298,558; 5,711,076; 5,134,775; 6,301,785; U.S. Patent Publ. Nos. 2009/0223057, 2004/181943, 2006/0225285, and 2006/0272155, 2008/060201A1; and WO 2011/047211. Some shaving aids contain one or more types of polyethylene oxide (PEO) with water insoluble polymers such as polystyrene.
One problem with the use of polystyrene is that it requires high processing temperatures during extrusion. The high processing temperatures can adversely impact the integrity of chemicals in the shaving aids potentially degrading them which can possibly impact consumer experience during use or product life cycle. The processing conditions required when using polystyrene can also limit what ingredients can be incorporated into the shaving aid as certain materials cannot be subjected to such temperatures or processing conditions.
Use of ethylene vinyl acetate as a water insoluble polymer has also been suggested. See e.g. U.S. Pat. Nos. 5,349,750, 5,454,164, and 5,551,152. Though ethylene vinyl acetate has been generally described as a potential water insoluble polymer for use in a shaving aid, many factors, including level of ingredients, grade of ethylene vinyl acetate, and processing conditions can impact the suitability of the shaving aid for actual use. U.S. Pat. No. 5,551,152, for example mentions shaving aid composites which can have 10-50% ethylene vinyl acetate and 50-90% of shaving aid material, with commercial grades of vinyl acetate ranging in vinyl acetate content from 5-50% by weight. This reference goes on to provide several examples of shaving aids with vinyl acetate having vinyl acetate content at 25% (Elvax 360).
Despite the earlier attempts, there remains a need for shaving aids that provide the right amount of lubrication and consistent lubrication over multiple uses where the product retains a sufficient effective lifespan (which can include structural integrity and/or ability of the shaving aid to continue providing a certain degree of lubrication after multiple uses). This is a significant challenge given shaving conditions vary by user based on individual shaving habit and environmental conditions; when designing products that are robust and can provide desirable lubrication yet retain structural integrity over multi-uses (in some instances up to 6 shaves, even as much as 12 shaves).
As such, there remains a need for a new shaving aid which can be processed at a wider range of operating conditions, particularly when considering extrusion type methods but still provide desirable lubrication over the life of the product. These and other benefits may be addressed by one or more embodiments of the following invention.